Morris co-wrote "Girl" alongside Sarah Aarons -- who also co-penned "The Middle," the country star's 2018 crossover smash collaboration with producer Zedd and electronic duo Grey -- as well as Greg Kurstin. Kurstin also has credit for producing the new song, which Morris says was inspired by a letter she was trying to write to a friend when their relationship was on the rocks.

"It felt like such a timely song for now," Morris tells ABC. "[In the letter, I was asking], 'Why are we competing against one another? Is it ourselves? Is it this industry? Is it the world?'" -- and then, she realized: "I don't think I am writing this to her. I am writing this to myself."

"Girl, don't hang your head low / Don't lose your halo / Everyone's gonna be okay, baby, girl," Morris sings in the new release, which is her fifth career single and the first taste of her forthcoming sophomore album. That project is due out later in 2019 and follows her critically acclaimed 2016 studio debut, Hero.

Morris first hinted that she was in the studio working on a new project in April of 2018, and over the course of the year, she teased a few new songs in her live shows, including "Flavor" and "To Hell and Back."

In mid-November, Morris posted a snapshot of herself and her manager listening to the finished project, which she nicknamed "MM2." "This album is my proudest work," she wrote alongside the photo. "All the ugly, all the things that shouldn't be said and SHOULD be said. We've been through it all. Y'all ain't ready."

The release of "Girl" comes on almost exactly the three-year anniversary of the release of Morris' breakout debut single, "My Church." That song was released on Jan. 19, 2016.